In the past two decades, there has been growing interest in new types of chemically sensitive devices based on the photolithographic batch processing employed by the semiconductor industry. This article reviews several classes of chemical sensors including electrochemicaldevices based on potentiometry and amperometry, chemical sensors based on thermal processes, and acoustic wavedevices.Devices based on dielectric property variation, the core of spectroscopy, are not treated here since many reviews of these topics are available. The article touches on the device principles and reviews some of the more recent developments in each class.

A simple, inexpensive method for precisely calibrating high resolution, pulsed dye lasers in the 500–340‐nm wavelength region has been devised. The residual portion of the laser beam exiting from an experiment is Raman shifted to longer wavelnegths in a high‐pressure hydrogen cell. The Stokes shifted output is used to excite laser induced fluorescence(LIF) signals in I2 vapor, which, in turn, are used to accurately calibrate the wavelength of the Raman shifted beam. The constant Raman shift, which can be precisely calculated, is then added to give the original laser wavelength. The method is readily adapted to computerized data acquisition and gives results of comparable accuracy to those of I2LIFcalibrations in the conventional 850–500 nm region.

This paper describes a tunable far‐infrared (FIR) spectrometer. Tunable radiation is obtained by frequency mixing, fixed frequency FIR laserradiation and tunable microwave radiation in Schottky barrierdiodes. An optically pumped laser and an HCN discharge laser are used as FIR sources and klystrons in the frequency range of 22–114 GHz as microwave sources. This yields an 85% coverage of the frequency region between 550 and 2700 GHz. Up to sixth order sidebands have been generated and used for spectroscopy. The ultimate sensitivity corresponds to a minimum detectable fractional absorption of 10−5 at 1‐s RC time. The applicability of the spectrometer in high‐resolution spectroscopy of transient species has been demonstrated by the observation of spectra of OD and N2H+. New laser emissions of optically pumped CH2F2 have been found and accurate frequencies have been determined for some of them.

A low pass filter is described that suppresses higher‐order diffraction light from vacuum ultraviolet and soft x‐ray monochromators. It consists of a triple siliconreflector with the angle of incidence matched to the desired photon energy cutoff. The performance is calculated and tested experimentally using a toroidal gratingmonochromator.

A computer‐based controller/averager has been built for the Balle‐Flygare pulsed nozzle, Fourier transform,microwave spectrometer. We have integrated gas and microwave pulse control, digitizing and averaging, signal processing, and mirror and frequency control into an IBM PC‐AT, allowing the computer to coordinate all processes in the spectrometer. Multiple free induction decays (FIDs) are recorded for a single gas pulse without delay between digitizing sequences by continuously clocking the FID’s into multiple segments of digitizer memory. The averager fits into one of the AT’s expansion slots and has the unique feature of sharing 16 kbyte of static memory with the CPU. This gives the computer immediate access to the current average since it is already in the computer’s memory. The averaging is very fast so that the nozzle and vacuum pump remain the limiting factors for the repetition rate. Programming features are described. The spectrometer is now easier and faster to run. The increased speed and multiple FIDs per gas shot improve the signal‐to‐noise ratio, thus improving the chances of finding weak transitions. It is possible now to make automated searches for new transitions.

A laser‐driven picosecond time‐resolved electron diffraction system operating in ultrahigh vacuum is described. A picosecond laser pulse is split into two beams. The first interacts with the sample under study. The second activates the cathode of an electron gun creating a collimated and focused electron pulse that is well synchronized with the heating laser pulse. By spatially delaying the part of the laser pulse that photoactivates the cathode from that which irradiates the sample, the electron pulse can be set to arrive at the sample at a specific time after sample irradiation. When a flat smooth sample is aligned such that the electrons are in grazing incidence on its surface, a reflection high‐energy electron diffractionpattern of its first few atomic layers is generated. Analysis of the diffraction pattern provides information on the surface structure and temperature at a set time lapse between the arrival of the laser and the electron pulse to the sample. Design, characterization, and operation of this system along with an example of its application to monitor the transient surface temperature using the surface Debye–Waller effect are discussed.

A new design high‐efficiency microchannel‐plate detector and amplification system is described for use in the scanning electron microscope. This complete detector system consists of four basic units: (1) the microchannel‐plate detector; (2) the video amplifier; (3) the high‐voltage power supply; and (4) the control unit. The microchannel‐plate detector system is efficient at both high and low accelerating voltages, and is capable of both secondary electron and backscattered electron detection modes. The size of the actual detector is approximately 3.5 mm in thickness and 25.4 mm in diameter. Thus, use of this detector system permits using almost all the sample chamber to accommodate large specimens with only the loss of the 3.5 mm of working distance. Another feature is that this system also employs a unique video amplifier where there are no active elements at high voltage. The microchannel‐plate detector system enables the investigation of secondary electron induced contrast mechanisms and backscattered electron detection at extremely low accelerating voltages even those below 1.0 keV.

A simple, endoscopic automatic vision system, using white‐light illumination has been designed and is discussed. Results of an application to the monitoring of the laying of an adhesive strip in a robotically operated product assembly are illustrated.

We have constructed a new scanning tunneling microscope(STM) using two mechanical stages. One (z stage) is for approaching the tip to the sample surface and the other (x stage) is for one‐dimensional movement of the sample to observe a specific area of the sample surface. The stages move so precisely that the distance between the tip and the sample is constant during the sample movement. It enables us to find the specific area quickly. Another feature of the STM is a novel data accessing method which realizes high‐speed scanning tunneling spectroscopy (STS) measurement. A great deal of data are accessed at high speed by a personal computer equipped with 32‐megabyte random access memory (RAM). Using this system, STM and STS measurements of cleaved (110) surfaces of Ga0.47In0.53 As/InP multiquantum wells were performed in air.

A new data acquisition and analysis system for scanning tunneling microscopy has been developed. With a single system, topography studies and current imaging tunneling spectroscopy can be performed, nanometer‐scale indentations can be made, and the off‐line analysis can be done. The system is based on the parallel use of several processors allowing for simultaneous data acquisition, processing, and display. User interfacing is done only via a host computer, a UNIX system with three‐dimensional display capabilities, while the measurements and indentations are done via a second processor with optimal real‐time characteristics.

A Fourier transformmass spectrometer(FTMS) for ultrahigh‐vacuum surface studies is described. The instrument incorporates standard surfaceanalysis techniques such as Auger electron spectroscopy(AES), low‐energy electron diffraction (LEED), and Ar ion sputtering, along with laser‐induced thermal desorption (LITD) and thermal desorption spectroscopy (TDS) using FTMS detection, to perform surfaceanalysis of metal samples. The manipulator allows temperature control of the samples between 110 and 1300 K. Using the LITD/FTMS surface reaction intermediates and kinetics are studied for the dehydrogenation of ethylene and cyclohexane on Pt(111). Relative sensitivities between AES and LITD/FTMS are discussed.

An improved bevel cross‐sectioning method is presented which makes it possible to measure the thickness of relatively thin semiconductor surface layers. A staining procedure to enhance the contrast of the layers for two material systems, GaAs/GaAlAs and InP/InGaAsP, has been developed. Applying a newly constructed ball‐lapping‐apparatus, an ordinary optical microscope and a surface‐profiler, relatively thin MBE‐grown quantum‐well layers (6.5 nm) can rapidly be measured with an accuracy of better than 10%, which is improved for thicker, normal layers (1000 nm) to better than 5%.

A technique for producing a tunable monodispersed spray is developed with a combination of impulsed jet and charging techniques. A single orifice impulse‐jet droplet generator, of a unique configuration, was used to produce a single stream of uniform droplets over a wide range of diameters. The single stream of droplets is dispersed with an electrostatic charging technique. Control of drop number density was enhanced by a droplet selection technique, in which a number of drops could be removed from the spray.

Effect of primary electron distribution on ion species yield is studied using a semicylindrical, multicusp plasma generator. Experimentally obtained, ion species yields were correlated with primary electron orbits estimated by computer simulation in several magnetic field configurations, where primary electron distributions were considered to be different. The result showed that a magnetic field configuration which produced lower proton yield had denser primary electron orbits in the neighborhood of the plasma grid. The floating potential of the plasma grid was also measured to suppose a distribution of the primary electrons. As a result, the proton yield increases with an increase of the floating potential of the plasma grid. These results lead us to confirm that the proton yield is determined by distribution of the primary electrons in the neighborhood of the plasma grid, in addition to the ratio of the plasma volume and the effective ion loss area. The highest proton yield of 93% and the lowest proton yield of 83% were obtained at the floating potential of the plasma grid of −5 and −21 V with respect to the anode potential, respectively, at an extraction current density of 150 mA/cm2.

A diagnostic for measuring the spectra of 3‐MeV protons and 1‐MeV tritons from DDfusion reactions in a tokamak has been developed. The emphasis in this work was on obtaining an energy resolution high enough to get information on the ion energy distribution from the energy spectra of the charged fusion reaction products. This low‐noise system allowed the first direct measurement of the spectra of 1‐MeV tritons from a tokamak. The diagnostic system is described, and measurements of the ion temperature and spectra resulting from non‐Maxwellian ion distributions are presented. Rotating the detector from shot to shot to get different lines of sight, it is even possible to obtain an emission profile of the fusion reaction products.

The hyperbolic energy analyzer (HEA) is based on a novel diagnostic principle which uses a new type of electrostatic lens. The HEA has a pinhole aperture, a hyperbolic lens, and a long Faraday cup. The hyperboloid cones which make up the lens have a vertex angle of 70.53°. Each cone is held at a constant potential. The hyperbolic lens performs two functions: it focuses the ions in space and it selects the ion energy which is collected by the Faraday cup. The HEA measured electron and ion characteristics in the M4X (modified Missouri magnetic mirror experiment) and the results were confirmed with Langmuir probes and ion energy analyzers.

This article discusses improvements in the efficiency, output power, and operational flexibility of MEDEA II, a double‐pulse electron beam accelerator at McDonnell Douglas Research Laboratories. A modified charging circuit, based on the triple‐resonance pulse transformer concept, was implemented on both of MEDEA II’s two stages. The output switches were modified to increase maximum output voltages, and a new, second output switch with asymmetric breakdown characteristics was developed. To avoid degradation of the second‐pulse output waveform at the diode, a keep‐alive circuit was installed. The effects of diode closure on double‐pulse operation are also discussed.

Although the measurement of Allan variance of oscillators is well documented, there is a need for a simplified system for finding the degradation of phase noise and Allan variance step‐by‐step through a system. This article describes an instrumentation system for simultaneous measurement of additive phase noise and degradation in Allan variance through a transmitter system. Also included are measurements of a 20‐kW X‐band transmitter showing the effect of adding a pass tube regulator.

Additions to commercially available manipulators are described which allow independent rotations of a sample in ultrahigh vacuum around three mutually perpendicular axes, as well as insitu adjustments of the sample orientation with respect to any of the three rotation axes. The additions allow also the interchange of three different samples insitu, with no need for breaking the vacuum in the experimental chamber. The modified manipulator has been successfully tested in experiments involving low‐energy electron diffraction and photoemission with synchrotron light for either s or s‐ppolarization geometries.